Casey Stoner, the most successful MotoGP rider since 2006, dropped a bombshell on the motorcycle racing world by announcing that he will retire at the end of the 2012 season.

The 26-year-old Double World Champion, who denied retirement rumors at the previous Estoril round, made the shock announcement during the pre-event press conference ahead of this weekend's French Grand Prix at Le Mans.

The Australian has been a full time grand prix rider since 2002, winning twice in 125cc, five times in 250cc and 35 times since moving to MotoGP in 2006.

Stoner won Ducati's only MotoGP title at his first attempt in 2007, then won his second world crown after switching to Repsol Honda for 2011.

Stoner, who currently leads the 2012 MotoGP standings by one point over Yamaha's Jorge Lorenzo, became a father for the first time just before the start of this season.

Seven time MotoGP champion Valentino Rossi used the same press conference to again insist that he will race on for at least another two years, despite a report claiming that he would retire at the end of the year.

Rossi and fellow world champion Lorenzo both said that Stoner's departure will be a big loss for the sport.